1. Technical Field
The present invention relates to a robot hand that can grip an object.
2. Related Art
According to the progress of robot technologies in recent years, industrial robots are used in most of manufacturing sites of industrial products. For example, in an assembly line for industrial products, it is a widespread practice to set plural industrial robots along the line and assemble various components to a product under manufacturing carried on the line using the robots to improve manufacturing efficiency. When such components assembled by the robots are conveyed to a line side, it is a widespread practice to convey the components using robots to improve manufacturing efficiency of the entire factory.
The industrial robots used in the assembly line and the like in this way handle objects having various sizes and shapes in work for conveying a component and work for assembling the conveyed component to a product. Therefore, a section (a robot hand) with which a robot grips an object is required to have high universality that enables the robot hand to cope with various objects. Therefore, robot hands that can grip components having various sizes and shapes are proposed (JP-A-2000-117677 and JP-B-06-30862).
However, the proposed robot hands have a problem in that it is difficult to grip components having various sizes and shapes with sufficient gripping force. Reasons for the difficulty are as explained below. First, the robot hands grip an object by holding the object with plural finger sections provided to be generally opposed to one another. Therefore, it is possible to grip objects having various sizes (or shapes) by changing a distance between the finger sections according to the size of an object. However, the object is merely retained by friction force in a contact portion in a state in which the object is held between the finger sections. It goes without saying that the friction force can be increased if the finger sections are strongly pressed against the object. However, there is a limit in the increase in the friction force because it is likely that the surface of the object is damaged. After all, the object cannot be gripped with sufficient force. As a result, for example, when work for gripping some small component and assembling the component to something is performed, various problems could occur, for example, the gripped component is shifted by reaction applied to the component during the assembly and the component cannot be assembled.